bash-4.2$ ./mailbox 3
3 1
4 2
6 1
5 1
7 3
9 2

The result from thread 3 is 7 from 1 operations during 2 secs.
The result from thread 2 is 13 from 2 operations during 2 secs.
The result from thread 1 is 14 from 3 operations during 3 secs.
bash-4.2$ ./mailbox 3 nb
3 1
4 2
6 1
5 1
7 3
9 2

The result from thread 3 is 7 from 1 operations during 1 secs.
The result from thread 2 is 13 from 2 operations during 2 secs.
The result from thread 1 is 14 from 3 operations during 3 secs.
bash-4.2$ ./mailbox 5
6 4

The result from thread 1 is 0 from 0 operations during 0 secs.
The result from thread 2 is 0 from 0 operations during 0 secs.
The result from thread 3 is 0 from 0 operations during 0 secs.
The result from thread 5 is 0 from 0 operations during 0 secs.
The result from thread 4 is 6 from 1 operations during 1 secs.
bash-4.2$ ./mailbox 5 nb
6 4

The result from thread 2 is 0 from 0 operations during 0 secs.
The result from thread 5 is 0 from 0 operations during 0 secs.
The result from thread 1 is 0 from 0 operations during 0 secs.
The result from thread 3 is 0 from 0 operations during 0 secs.
The result from thread 4 is 6 from 1 operations during 1 secs.